This application claims the priority of British patent document 9919679.2, filed 20 Aug. 1999, the disclosure of which is expressly incorporated by reference herein.
This invention relates to a monitoring system that includes a monitor means arranged to display an image generated using an infrared detection means. The monitoring system according to the invention is suitable for use, among other applications, in a motor vehicle.
Infrared transducers, especially those in the 10 μm wavelength range, generate an image in grey values using the temperature distribution of objects and their background, typically with 8 bit resolution. For this purpose, there must be an assignment of a grey value to each temperature interval. The resulting signal, which may be video, can then be presented on a head-up display (HUD) or on a monitor as, for example, a black and white image.
The assignment of grey values to temperature intervals has generally been established such that brighter grey values relate to higher temperatures and darker grey values relate to lower temperatures. Using such an assignment of grey values, a person can usually be distinguished quite clearly against a background having a dark grey value. If, however, a user of a vehicle wishes to use such a system to detect the course of a road he is trying to follow, the colder street edgings/kerb stones and the road surface become the darker images and the warmer background of the roadside verges become brighter on the monitor or in the HUD.
It is a problem with some prior art systems that, depending on the extent of the temperature difference, this picture may prove to be contrary to the desired contrast for efficient road surface monitoring.
One attempt to overcome this problem is disclosed in European patent document EP 0 873 011, in which the grey values of a digital infrared camera are changed using correction parameters, based on a comparison of grey values to the average. This system, however, may not prove suitable for all driving situations and in addition does not give a user the option of choosing an assignment of grey values which suits his or her particular wishes or eye sight requirements.
It is an object of this invention to provide an improved monitoring system of the type described above.
This and other objects and advantages are achieved by the monitoring system according to the invention, which includes a monitor device arranged to display an infrared image, and which includes means for changing the assignment of grey values to the temperature of objects in the image in response to a user operated input. Such input may comprise a multi-position switch, each position of which is arranged to assign a different set of grey values to high and/or low temperatures; or alternatively, it may comprise a voice operated controller arranged to assign a different set of grey values to high and/or low temperatures in response to each of a pre-defined set of voice commands.
Additional changes may be made, or manual changes altered, automatically in response to a driving situation—assessment unit, which may include an input from a navigation.
The invention also provides a vehicle including a monitoring system according to the invention.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.